KDX420 Almost Ready to Ride

Member

Hey everyone,
It's been a long haul and quite a while since I posted on here last. I did a complete tear down and rebuild of my '81 KDX420 over the past year or so. Unfortunately, I get distracted with other things and had to put it aside for a while, but now I'm almost finished and need a bit of help with a carb problem.
I did a full rebuild on the carb and tried to make sure everything went back together the way it was supposed to, but I can't seem to get it to stop puking gas out of the bowl overflow vent. I set the float levels according to the specs in my clymer manual, but it just doesn't want to stop overflowing. Any thoughts or suggestions would be great.
I'm gonna try to include some pics of the ALMOST finished product.

Member

When I did the rebuild on the carb I only replaced the necessary gaskets and seals. I assumed everything would work as it had before I tore it apart. It was always a little tough to start cold, but always seemed to run fine after I got it going.
I have looked at the float valve assembly a few times assuming that maybe that's where the issue is, but is looks ok. The floats themselves appear ok also. Maybe my problem is just in the adjustment at the moment.

Member

Just got back from the garage again. I took the carb apart, removed the float valve assembly and made sure it was clean and free of defects. It looked fine of course the proof is in the pudding, so I put the body of the carb on with the bowl off so that I could press on the float valve with my finger. I attached the fuel line and opened the flow. I was able to control the fuel flow through the float valve just fine, so I don't believe the float valve is at fault. Next I filled the fuel bowl by itself to make sure the floats were actually floating.....no problems there either.
I adjusted the tabs for the float contacts down a bit further and retried the whole thing again, but it's still puking out of the bowl vent.
The tabs on the float lever can be installed 2 different ways, which is what I thought I screwed up from the very beginning, but in the pic taken from my clymer manual, it clearly shows the tabs stepped upward towards the top of the carb (since the carb in the pic is upside down) which is exactly the way I installed mine. Is is possible that this info is incorrect? I have no reference to go by except the book. Any thoughts out there people? It would really help me out.

Member

Can't tell. The floats on this 420 ride on posts inside the bowl and are independent of each other and the float lever. The only way to see if they would hit something would be to put the bowl back on the body of the carb and then of course it's impossible to see inside to see what they're doing.

Member

Anybody out there got any thoughts or suggestions on this carb issue? I'm gonna head out to the garage and start adjusting the float lever until it stops leaking out the vent or I can't adjust it any further.

Member

ok, I guess I found another major issue on this bike. The last person to use it was my brother a few years ago and after he returned it to me I never fired it up again, just assumed it was still working other than the brake and clutch levers he broke. Turns out the best I can get out of the engine is just shy of 50psi on a compression test. I don't know that much about 2 strokes but I'm pretty sure that's not good. The clymer manual makes mention of anything below 100psi being bad.
As for the carb, adjusted the float level to a point where it stopped leaking....at least I thought it had, came back about a half hour later and it was starting to drip out of the bowl vent again.....ARGH! This things driving me nuts.

Any suggestions on a plan of attack for the engine? Am I looking at a total rebuild here or are they prone to certain issues I should be looking for with low compression? Not sure how willing I am to keep dumping money into this thing.